This is a project work from department of mechanical Engineering,KUET

1. Design & Construction of a Universal Coupling
A project report submitted to the department of Mechanical Engineering, Khulna university
of Engineering & Technology in partial fulfillment of the requirements for the
“Course of ME-3118”
Supervised by Submitted by
Md. Rasedul Islam Antu Datta
Lecturer, Roll No: 1205001
Department of Mechanical Engineering Zulfikar Habib Khan
Khulna University of Engineering & Technology Roll No: 1205003
Md. Shariful Islam
Roll No: 1205004
Sudip Saha
Roll No: 1205005
June 2015
Department of Mechanical Engineering
Khulna University of Engineering & Technology
Khulna-9203, Bangladesh

2. i
Acknowledgements
All the praises to the almighty who makes authors capable to complete this project work
successfully. The authors are very much indebted to their course teachers Md.Golam Kader ,
professor of department of Mechanical Engineering, Khulna University of engineering &
technology, Bangladesh, and Md. Rasedul Islam ,Lecturer of department of Mechanical
Engineering, Khulna University of engineering & technology, Bangladesh, for their wise
inspiration to do such extraordinary project work. The authors express the heart- felt respect to
them for their proper guidance and all kind of support to perform and complete this special work.
The authors are extremely grateful to Prof. Dr. Nawsher Ali Moral ,Head of the department
of mechanical engineering Khulna University of engineering & technology, Bangladesh, to
provide such a good opportunity to do the experimental work and for providing all other
supports.
May ALLAH bless both of the course teachers.
“Authors”

3. ii
Abstract
A coupling is a device used to connect two shafts together at their ends for the purpose of
transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment
while permitting some degree of misalignment or end movement or both.
A Universal coupling is a special type of coupling in which misalignment of shafts is allowed.
Shafts are free to move any direction in order to transmit torque or power from one shaft to
another.
In this project work a Universal coupling was designed, in which safe torque on shafts and pin
size of cross determined.
Finally the Universal coupling made by Mild Steel, which is low cost and available in every
workshop.

4. iii
CONTENTS
Page
Acknowledgement………………………………………………………………….…………i
Abstract…………………………………………………………………………….….………ii
List of Figures…………………………………………………………………………………v
List of Tables………………………………………………………………………………….vi
Nomenclature…………………………...………………………………………….…………vii
CHAPTER-І: INTRODUCTION
1.1 Introduction………………………………………………………………………………..2
1.2 Objectives……………………………………………………….…………………………3
CHAPTER-ІІ: LITERATURE REVIEW
2.1 Historical Background…………………………………………….…………………..........5
2.2 Coupling…………..…………………………………….……………….…….……………5
2.3 Types of coupling…………….………………………………………….………………….5
2.4 Rigid Couplings …………………………………………………………….………....……6
2.5 Flexible couplings …………………………………………………………………….…….6
2.6 Miscellaneous Couplings ………………………………………………………………..….7
2.7 Universal Coupling or Hooke’s coupling …………………………….…………………..…8
2.8 A simple brief about U joint……………………………………………………..................9
2.9 Types of Universal coupling…………………………………………….……………….…..9
2.9.1 Single joints Universal coupling…………………………………….……………..10
2.9.2 Double joints Universal coupling………………………………….………………10
2.9.3 Assembled joints Universal coupling…………………………………...…………10
2.10 Field of Applications of Universal Coupling………………………………………………11

5. iv
CHAPTER-ІІІ:
3.1 Introduction ………………………………………………...………….…………………12
3.2 Problem………………………………………..………….………….……………………12
3.3 Solution……………………………………………….………….………….…………….14
3.4 Our Designed dimension………………………………………………..…………………16
3.5 CAD design and Rendered view…………………………………..………….…………..17
3.6 Material………………………………………………..………..………………………….18
3.7 Selection Guide………………………………………………..………….………………..18
CHAPTER-ІV:
4.1 Machine & Apparatus Required………………………..………………..………………..20
4.2 Machining Processes…………………………………..………………..…………………20
4.2.1 Drafting…………………..………………..………………..…………….……20
4.2.2 Gas Cutting……………………………………………………………………20
4.2.3 Facing…………………………..………………..…………………………….21
4.2.4 Turning………………………………..………………..………………………21
4.2.5 Grinding…………………………………………..………………..…………21
4.2.6 Drilling………………………..………………..………………..…………….22
4.3 FINAL PROJECT……………………………………………………………………….23
CHAPTER-V
5.1 Discussion……………………………………………………………………….……..25
5.2 Conclusion…………….……………………………………………………………….25
References………………………………………………………………………….…….26

6. v
LIST OF FIGURES
Figure Title Page
Figure-1.1 Different types of alignment……………………………...2
Figure-2.1 Flanged Coupling…………………………………………6
Figure-2.2 Muff coupling …………………………………………….6
Figure-2.3 Flanged Pin Bush Couplings ……………………………..7
Figure-2.4 Gear Tooth Coupling ……………………………………..7
Figure-2.5 Oldham’s Coupling …………………………….………....7
Figure-2.6 Universal Coupling ……………………………….………7
Figure-2.7 Jaw type coupling …………………………………………8
Figure-2.8 Sleeve type coupling………………………………….……8
Figure-2.9 Universal Coupling ………………………………………..8
Figure-2.10 A simple brief about U joint………………………………9
Figure-2.11 Single Joint……………………………………………….10
Figure-2.12 Double joint ………………………………………………10
Figure-2.13 Telescopic Joint ……………………………………….….10
Figure-3.1 Problem fig………………………………………………..13
Figure-3.2 Solution fig………………………………………….….…14
Figure-3.3 Dimensions of the cross………………………….……….16
Figure-3.4 Dimensions of the shaft…………………………….…….16
Figure-3.5 CAD design………………………………………..…..…17
Figure-3.6 Rendered view of CAD design……………………...…...17
Figure-4.1 A typical draft ………………………………….………..20

7. vi
Figure-4.2 Gas Cutting………………………………………………20
Figure-4.3 facing operation on Lathe machine………………...….…21
Figure-4.4 Turning operation on Lathe machine……………………21
Figure-4.5 Grinding operation………………………………………21
Figure-4.6 Drilling operation………………………………….……21
Figure-4.7 Designed product……………………………..…………23
LIST OF TABLES
Table Title Page
Table-3.7 Selection Guide………………………………..…18

8. vii
NOMENCLATURE
Symbol Description
Ns2 …………………………………………………. Angular velocity of the driven shaft
Ns1 ………………………………………………… Angular velocity of the driver shaft
Θ…………………………………………………….Angle between axes of the shafts
α………………………………………………….... Angle of the driving shaft from the position
where the pins of the drive shaft yoke are
F…………………………………………………….Force
M……………………………………………………Torque applied to shaft
Sb………………………..………………………….Bearing stress
Ss…………………………………………………..Transverse shear stress
Sc……………………………………………….….Compressive stress
A…………………………………………………...Cross-sectional area of pin
d………………………………………………...…Diameter of pin
I……………………………………….……….….Mass moment of inertia

9. 1
Chapter One:
 Introduction
 Objectives

10. 2
1.1 Introduction:
Couplings are mechanical elements that ‘couples’ two drive elements which enables motion
to be transferred from one element to another. The drive elements are normally shafts. We
tend to see lot of applications of the couplings mainly in the automobiles, for example the
drive shaft which connects the engine and the rear axle in a bus or any automobile is
connected by means of a universal joint.[1]
The primary purpose of couplings is to join two pieces of rotating equipment while
permitting some degree of misalignment or end movement or both. By careful selection,
installation and maintenance of couplings, substantial savings can be made in reduced
maintenance costs and downtime.
There are various types of coupling based on area of application and misalignment or degree
of freedom to move in any direction. Such as the universal coupling allows the shafts to
move in any directions. The different types of alignments are:[2]
Fig.1.1: Different types of alignment
Details about different types of coupling will be discussed latter.

11. 3
1.2 objectives:
The main objectivesof this project work are-
I. To solve a problem related to Universal coupling
II. To design that problem
III. To calculate the safe torque on shaft.
IV. To know about its application.

12. 4
Chapter Two:
 Historical Background
 Coupling
 Types of coupling
 Rigid Couplings
 Flexible or Compensating Couplings
 Miscellaneous Couplings
 Universal Coupling or Hooke’s Coupling
 A simple brief about Universal Coupling
 Types of Universal coupling
 Field of Applications of Universal Coupling

13. 5
2.1: Historical Background:
The main concept of the universal joint is based on the design of gimbals, which have been in
use since antiquity. The first person known to have suggested its use for transmitting motive
power was GerolamoCardano, an Italian mathematician, in 1545, although it is unclear whether
he produced a working model. In Europe, the device is often called the Cardan joint or Cardan
shaft. Christopher Polhem of Sweden later reinvented it, giving rise to the name Polhemsknut in
Swedish.
Gaspar Schott ((1664), who called it the paradoxum, but mistakenly claimed that it was
a constant-velocity joint. Shortly afterwards, between 1667 and 1675, Robert Hooke analysed the
joint and found that its speed of rotation was nonuniform, but that this property could be used to
track the motion of the shadow on the face of a sundial. The first recorded use of the
term universal joint for this device was by Hooke in 1676, in his book Helioscopes. He
published a description in 1678, resulting in the use of the term Hooke's joint in the English-
speaking world. In 1683, Hooke proposed a solution to the non-uniform rotary speed of the
universal joint: a pair of Hooke's joints 90° out of phase at either end of an intermediate shaft, an
arrangement that is now known as a type of constant-velocity joint.
The term universal joint was used in the 18th centuryand was in common use in the 19th century.
19th century uses of universal joints spanned a wide range of applications. Numerous universal
joints were used to link the control shafts of the Northumberland telescope at Cambridge
University in 1843. The term Cardan joint appears to be a latecomer to the English language.[3]
2.2 Coupling:
Couplings are mechanical elements that ‘couples’ two drive elements which enables motion to
be transferred from one element to another. The drive elements are normally shafts.Couplings
are used to connect two shafts for torque transmission in varied applications. It may be to
connect two units such as a motor and a generator or it may be to form a long line shaft by
connecting shafts of standard lengths say 6-8m by couplings.
2.3 Types of coupling:
Based on the area of applications there are various types of coupling available. But they are
generally categorized in the following varieties-[1]

14. 6
i. Rigid Couplings
ii .Flexible or Compensating Couplings
iii. Miscellaneous Couplings
2.4 Rigid Couplings:
Rigid Couplings are mainly used in areas where the two shafts are coaxial to each other. There
are many types of couplings that fall under the rigid couplings category. They are
i. Flanged Coupling
ii. Muff coupling
Fig 2.1: Flanged Coupling Fig 2.2 : Muff coupling
2.5 Flexible or Compensating Couplings :
Flexible couplings are normally used in areas where the coaxiallity between the connecting
shafts is not always assured and in areas where there is a possibility of occurrence of shocks in
the transmission is applicable. They are also called as Elastic Couplings. By construction these
couplings tend to have an elastic member in between the two connecting entities. The different
types of flexible couplings are
i.Flanged Pin Bush Couplings
ii. Bibbly Coupling
iii. Gear Tooth Coupling
iv. Tyre couplings

15. 7
v. Elastomeric Couplings
vi. Oldhams Coupling
vii. Universal Coupling or Hooke’s Coupling (OUR CONCERN)
2.6 Miscellaneous Couplings:
This group of couplings incorporate design features which are frequently unique,approximations
or combiations of universal,Oldham and flexible shaft couplings.such as- Jaw type coupling
and Sleeve type coupling.

16. 8
2.7 Universal Coupling or Hooke’s coupling:
A universal joint, (universal coupling, U-joint, Cardan joint, Hardy-Spicer joint, or Hooke's
joint) is a joint or coupling that allows the shafts to 'bend' in any direction, and is commonly
used in shafts that transmit rotary motion. It consists of a pair of hinges located close together,
oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant
velocity joint.
Fig 2.9: Universal Coupling

17. 9
2.8 A simple brief about Universal Coupling:
A universal joint is like a ball and socket joint that constrains an extra degree of rotational
freedom. Given axis 1 on body 1, and axis 2 on body 2 that is perpendicular to axis 1, it keeps
them perpendicular. In other words, rotation of the two bodies about the direction perpendicular
to the two axes will be equal.
In the picture, the two bodies are joined together by a cross. Axis 1 is attached to body 1, and
axis 2 is attached to body 2. The cross keeps these axes at 90 degrees, so if you grab body 1 and
twist it, body 2 will twist as well.
A Universal joint is equivalent to a hinge-2 joint where the hinge-2's axes are perpendicular to
each other, and with a perfectly rigid connection in place of the suspension.
Universal joints show up in cars, where the engine causes a shaft, the drive shaft, to rotate along
its own axis. At some point you'd like to change the direction of the shaft. The problem is, if you
just bend the shaft, then the part after the bend won't rotate about its own axis. So if you cut it at
the bend location and insert a universal joint, you can use the constraint to force the second shaft
to rotate about the same angle as the first shaft.[4]
Fig 2.10: A simple brief about U joint
2.9 Types of Universal coupling:
The universal couplings are categorized as-[5]
i. Single joints

18. 10
ii. Double joints
iii.Telescopic or assembled joints
2.9.1 Single joints Universal coupling:
Precision single joints suit angles up to 45° and speeds to 4000 r/min. Shaft sizes 6 to 50 mm,
dimensions to DIN 808.
Fig 2.11: Single Joint Fig 2.12: Double joint
2.9.2 Double joints Universal coupling:
Precision double joints suit angles up to 90° and give constant velocity output. Shaft sizes 6 to 50
mm, dimensions to DIN 808.
2.9.3 Assembled joints Universal coupling:
Telescopic universal joint with plain bearings either to standard lengths or customised to your
requirements. Angles up to 45° per joint and speeds to 1000 r/min, Type HA offers higher
speeds.

19. 11
Fig 2.13: Telescopic Joint
2.10 Field of Applications of Universal Coupling:
Typical applications of universal joints include-
 AUTOMOBILE
 Aircraft
 Appliances
 Control mechanisms
 Electronics instruments
 Medical & optical devices
 Ordinance radio
 Sewing machines
 Textile machineries etc.

20. 12
Chapter Three:
 Introduction
 Problem
 Solution
 Our Designed dimension
 CAD design and Rendered view
 Material
 Selection Guide
3.1 Introduction:
To design is either to formulate a plan for the satisfaction of a specified need or to solve a
problem. If the plan results in the creation of something having a physical reality, then the
product must be functional, safe, reliable, competitive, usable, manufacturable, and marketable.
Design is an innovative and highly iterative process. It is also a decision-making process.
Decisions sometimes have to be made with too little information, occasion-ally with just the
right amount of information, or with an excess of partially contradictory information. Decisions
are sometimes made tentatively, with the right reserved to adjust as more becomes known. The
point is that the engineering designer has to be personally comfortable with a decision-making,
problem-solving role.[6]
3.2 Problem:[7]
A universal coupling (universal joint, or Hooke’s joint) is used to connect two shafts which
intersect but which are not necessarily in the same straight line, as shown in Fig below. The
angular velocity of the output shaft is not equal to the angular velocity of the input shaft, unless
the input and output shafts are in line. The ratio of speeds is given by
Ns2
Ns1
=
cosθ
1 − Cos2αSin2θ
Where
Ns2 = angular velocity of the driven shaft

21. 13
Ns1 = angular velocity of the driver shaft
θ=angle between axes of the shafts
α= angle of the driving shaft from the position where the pins of the drive shaft yoke are in the
plane of the two shafts.
A torque of 40N m is applied to shaft S1 of a universal joint in which S1 and the output shaft S2
are in the same horizontal plane.
Fig 3.1: Problem fig
a. Determine the torque on shaft S2 for the position shown in Fig.
b. Determine the size of the pins of the connecting cross for an allowable bearing stress of
14 MPa (per projected area), an allowable bending stress of 140 MPa, and an allowable
shear stress of 70 MPa.
c. Calculate the maximum shear stress on section E-E, which is 50 m from axis Y-Y.

22. 14
3.3 Solution:
(a)
The components of F, acting on the shaft S1, are
F cos200
and F sin200
.
The troque acting on the shaft S1 due to the action of the cross is
Mt= ( F cos200
)(0.05)
or, 40 = ( F cos200
)(0.05)
or, F = 851N
The torque on the shaft S2 is
0.05 =(851)(0.05) = 42.6 Nm. (Ans.)
Fig 3.2: Solution fig

23. 15
(b)
(1) The size of the pins will depend on the maximum load, which occurs for the position
shown.
The maximum pin load is 851N.
Diameter of pin based on bearing:
sb =
or, 140 * 106
=
.
or, d = 10 mm
(2) Diameter of pin bending on based:
s =
or, 140 * 106
=
∗ , ( )
or, d = 7.2 mm
(3) Diameter of pin based on transverse shear:
Ss = 4
3 *
or, 70 * 106
= (4
3)(851
2
)
or, d = 4.6 mm
Therefore bearing dictates the minimum size of pin; a 10mm diameter pin should be
satisfactory.
(c)Maximum compressive stress at section E-E is
Sc = + =
∗ , ∗ .
. ∗( . ) /
+ . ∗ .
= 65.9 MPa
Maximum shear = * (65.9) = 33 Mpa (Ans.)

24. 16
3.4 Our Designed dimension:
Fig 3.3: Dimension of the cross
Fig 3.4: Dimensions of the shaft

25. 17
3.5 CAD design and Rendered view:
Fig 3.5: Cad design of universal coupling
Fig 3.6: Rendered view of the cad design

26. 18
3.6 Material:
Considering cost, strength, ease of access taken into account the selected material for this design
is MILD STEEL.
3.7 Selection Guide:[5]

27. 19
Chapter Four:
 Machine & Apparatus Required
 Machining Process
 Methodology
 Final Project

28. 20
4.1 Machine & Apparatus Required:
 Lathe
 Drilling
 Grinding machine
 Welding apparatus
4.2 Machining Processes:
4.2.1 Drafting:It’s a pre-manufacturing process in which a replica of the designed
prototype is made.
Fig.4.1: A typical draft Fig 4.2: Gas Cutting
4.2.2 Gas Cutting: Oxy-fuel welding (commonly called oxyacetylene welding, oxy
welding, or gas welding in the U.S.) and oxy-fuel cutting are processes that use fuel gases and
oxygen to weld and cut metals, respectively.
The common methods used in cutting metal are oxygas flame cutting, air carbon-arc cutting, and
plasma-arc cutting. The method used depends on the type of metal to be cut and the availability
of equipment. As a Steelworker, oxygas or air carbon-arc equipment is the most common type of
equipment available for your use.

29. 21
4.2.3 Facing:Facing is the process of removing metal from the end of a work-piece to
produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can
face rectangular or odd-shaped work to form cubes and other non-cylindrical shapes.
Fig 4.3: facing operation on Lathe machine Fig 4.4: Turning operation on Lathe
machine
4.2.4 Turning:Turning is the removal of metal from the outer diameter of a rotating
cylindrical work-piece. Turning is used to reduce the diameter of the workpiece, usually to a
specified dimension, and to produce a smooth finish on the metal. Often the workpiece will be
turned so that adjacent sections have different diameters.
4.2.5 Grinding:Grinding is a finishing process used to improve surface finish, abrade hard
materials, and tighten the tolerance on flat and cylindrical surfaces by removing a small amount
of material. Information in this section is organized according to the subcategory links in the
menu bar to the left.
Fig.4.5:Grinding operation Fig 4.6:Drilling operation

30. 22
4.2.6 Drilling:Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of
circular cross-section in solid materials. The drill bit is a rotary cutting tool, often multipoint.
The bit is pressed against the workpiece and rotated at rates from hundreds to thousands
of revolutions per minute. This forces the cutting edge against the work-piece, cutting off chips
(swarf) from the hole as it is drilled.
4.3 Methodology:
Various Machines were used for several machining processes:-
I. Lathe machine was used for facing, turning.
II. Drilling machine was used for drilling & boring.
III. Grinding machine was used for surface finishing.
IV. Welding apparatus was used to connect different parts at the time of setting up.

31. 23
4.4 FINAL PROJECT:
Fig 4.7: Designed product

32. 24
Chapter Five:
 Discussion
 Conclusion

33. 25
5.1 Discussion:
Mechanical couplings have a principal use in the connection of rotating shafts for the transfer of
rotary motion and torque. As with all mechanical devices, a coupling must match its’ intended
purpose and application parameters, including many different performance, environmental, use
and service factors. There are various reasons for which a coupling fails, such as-improper
installation, excessive vibration, abnormal noise and chattering etc. The failure of coupling can
be minimized by proper maintenance, such as-checking and changing lubricant regularly,
performing visual inspection, checking signs of wear and fatigue and cleaning coupling
regularly etc.
5.2 Conclusion:
Mechanical design is a complex undertaking, requiring many skills. Design and fabrication of a
Universal coupling was done in this project work. In designing problem safe torque on shaft was
determined. The cross pin size (diameter) was determined considering bearing stress, shearing
stress and bending stress taken into account. The application of a universal coupling also studied
in this project work.

34. 26
References:
[1]: http://www.brighthubengineering.com/machine-design/43237-shaft-couplings-
types/#imgn_1
[2]:https://www.google.com.bd/search?q=types+of+misalignment&espv=2&biw=1093&bih=53
4&tbm=isch&imgil=NT3Hya-
mp4X71M%253A%253BWa1ZBFnm6w2zQM%253Bhttp%25253A%25252F%25252Fsdp-
si.com%25252FD757%25252Fcouplings1.htm&source=iu&pf=m&fir=NT3Hya-
mp4X71M%253A%252CWa1ZBFnm6w2zQM%252C_&usg=__Ctk4urH8tWcUMRt3asG7xLg
nZ1E%3D&ved=0CDoQyjc&ei=LQaFVfKnHY28uATA5YMg#imgrc=NT3Hya-
mp4X71M%253A%3BWa1ZBFnm6w2zQM%3Bhttp%253A%252F%252Fsdp-
si.com%252FD757%252FImages%252Ffig1.gif%3Bhttp%253A%252F%252Fsdp-
si.com%252FD757%252Fcouplings1.htm%3B550%3B250&usg=__Ctk4urH8tWcUMRt3asG7x
LgnZ1E%3D
[3]: Mills, Allan, "Robert Hooke's 'universal joint' and its application to sundials and the sundial-
clock", Notes & Records of the Royal Society, 2007, accessed online 2010-06-16
[4]: http://ode-wiki.org/wiki/index.php?title=Manual:_Joint_Types_and_Functions
[5]: http://www.techdrives.co.uk/Multimedia/Shaft%20Couplings/shaft-couplings-universal-
joints-feb13.pdf
[6]: Budynas−Nisbett,” Shigley’s Mechanical Engineering Design”, Eighth Edition, McGraw-
Hill, ISBN: 0−390−76487−6
[7]: Hall, Holowenko,Laughlin,”Theory and problems of Machine Design” ,SI metric edition,
Schaum’s outline series.